The present invention relates generally to a guide-pin for tracing templates and stencils when used on a permanently-set pantograph.
In the prior art as exemplified by U.S. Pat. No. 4,397,090 by the present inventor, tracing was effected by using pantographs having an adjustable sliding pivot mechanisms that had to be set.
In order to eliminate these pivot mechanisms when tracing images on a flat surface, the present inventor also previously devised a pantograph as shown in FIGS. 2 and 3 (but without the guide-pin). The pantograph is transparent and has a plurality of openings, each indicative of a different ratio for enlarging and reducing the size of the image.
The pantograph has four arms arranged to form a parallelogram having a pivot at each corner of the parallelogram, one of the arms constituting an enlarging ratio arm and another arm constituting a reducing ratio arm. The enlarging ratio arm has an extended portion which extends beyond a first pivot. This extended portion has a plurality of openings spaced apart from each other by unequal spacings. Each opening represents a different enlargement ratio, the values of which increase the further away from the pivot point the corresponding opening is located. The reducing ratio arm is pivoted at that same first pivot and has a plurality of openings spaced apart from each other by unequal spacings, each opening representing different reduction ratios with values that are reciprocals respectively of the enlargement ratios.
To enlarge a size of an original image, a desired proportion making opening of the enlarging ratio arm is placed over a planned image point. A corresponding reciprocable ratio opening in the reduction ratio arm is located over a corresponding original image point; this opening serves as a sight hole. The enlargement ratio arm is guided and moved relative to the other arms and an image is then marked while one concentrates on the original image being traced through the sight hole. A third arm, which is also pivoted with the enlargement ratio arm, should be fastened to the work surface.
To reduce the size of an original image, a mark is made through a selected ratio opening in the reduction ratio arm to draw a resized image while sighting and following the original image through the reciprocal ratio opening in the enlargement ratio arm. A guide knob can be secured to another opening in the enlargement ratio arm to better control the tracing. The third arm is also fastened to the work surface.
The fastening of the third arm can be effected by extending a shaft of a pivot tack through an end opening at an end of the third arm such that its tack head rests on top. The shaft is further inserted through a pivot base immediately underneath the end opening and into the work surface.
Alternatively, the shaft of the pivot tack is extended through the pivot base and through the end opening from the underside of the third arm. The shaft is then fed into a throughgoing hole in a pivot knob, which is made of elastic material and has a diameter smaller than that of the shaft of the pivot tack. The pivot base is taped to the working surface or, for brief enlarging operations, the guide knob is pressed down to retain this entire assembly in place against the working surface.